<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="http://cdn.staticfile.org/jquery/3.6.1/jquery.js"></script>
    <script>
        $(function(){
            $("button").click(function(){
                // $("ul").fadeToggle(1000)
                $("ul").toggle(1000)
            })
        })
    </script>
    <style>
        ul{
            width: 100px;
            background-color: rgb(128, 125, 121);
        }
    </style>
</head>
<body>
    <div>
        <button type="button" >指向我</button>

        <div>
            <ul>
                <li>one</li>
                <li>two</li>
                <li>three</li>
                <li>four</li>
            </ul>
        </div>
    </div>
</body>
</html>